It's a Wireless Timer Remote . You connect it to your camera, and you can set it to take pictures automatically at intervals of your choice. For example, I can set it to start shooting in 30 seconds from when I press the timer start button, and to take pictures every 3 seconds for 1 minute (or whichever interval or duration I choose) You simply set it, put your camera on a tripod or flat surface, press the timer start button and get in the picture! It will then take photos automatically every few seconds as you have programmed. This saves you from having to press a remote shutter each time you want to take a picture (or use the timer on your camera) just giving you a little bit more freedom to interact and get involved without having to worry about taking the picture.
The model I originally wanted was the Canon TC80N3 Timer Remote Control - but at $129, I simply couldn't justify the expense and was never going to buy it. Then I found this one, the YONGNUO MC-36R/C3 Wireless Timer Remote which at $22, is a more much purse friendly for an amateur. From what I can see this does exactly the same as the Canon version, but cheaper! I'm sure it's probably not as rugged as the Canon one but for the price it seems robust enough for my needs. This particular one fits the Canon 5D models, but you get ones with different connectors to fit the Canon Rebels or Nikon cameras for example.
I'll be setting it up to take some self portrait shots later this weekend so I'll share them with you when I do (if I can bear to have my double chin exposed on the internet) I had intended doing a test today, but I have just spent the last 30 minutes trying to figure out how to get it to work - although I could set the timer and everything seemed to be working, the camera just wouldn't fire. Twenty minutes later I realised that I had forgotten to plug the remote timer into the camera. I have obviously reached new depths of forgetfulness.
Have a great weekend!